Breast shield sets are used together with breast pumps for pumping off human breast milk. They usually comprise a breast shield with a breast shield funnel for placing on the human mother's breast, a first connector part for connection to a milk collection vessel, and a second connector part for attachment to a mechanical or electrical pump or for attachment to a suction line of such a pump.
To pump off the breast milk, the breast shield funnel is placed as tightly as possible on the mother's breast, and a vacuum is generated cyclically in the breast shield funnel by means of the pump. To keep the space to be evacuated as small as possible, i.e. to minimize the dead volume, the breast shield set has a nonreturn valve in the direction of the milk collection vessel. This nonreturn valve is opened toward the interior of the milk collection vessel by means of the pressure of the aspirated milk and, when a vacuum is applied, closes said vessel off relative to the evacuated volume of the rest of the breast shield set.
The valve has a valve seat which is covered by a valve body in the form of a diaphragm flap secured at one end. When the milk flowing in is at sufficient pressure, the diaphragm flap is opened toward the interior of the vessel. This valve has indeed proven effective in practice. However, such breast shield sets are relatively expensive to manufacture. Since the market increasingly requires that these breast shield sets should, for hygiene reasons, be used just once or at most only a few times, there is a need to reduce the manufacturing costs as much as possible.
Since these breast shield sets are therefore to be used only a few times at most, the individual parts should be able to be produced as inexpensively as possible. This applies also in particular to the nonreturn valve. Since, however, the breast shield set should be cleaned after each use, the valve must also be constructed as simply as possible and be correspondingly easy to clean. Moreover, it must not distort during cleaning, in order to subsequently ensure sufficient sealing. The shape, configuration and choice of material of the valve play an important role in achieving these objects. The breast shield sets are usually made from plastic, in particular polyethylene (PE), polypropylene (PP) or polycarbonate (PC), while the valve body itself is made of silicone.